Usually best price does not come with best service, and best service does not come with best price.
Thing is, what do you mean by best service?
Do you want people to call you "bro" the minute you walk in? Do you want the sales staff to let you try all the lenses for unlimited amount of time? Then, your best bet is John 3:16. But do note that people try try try, then the product is sold to someone. So if you buy something, maybe someone try try try before?
Do you want ok price so anyone walking in will get same quote? Do you want to look see look see in a store without anyone bothering you until you have a question? do you want staff who know their stuff and is honest to you if they know somewhere else sells it cheaper? Then Orient Photo and SLR Revolution is your best bet.
Do you want sales guys to run around for you? Do you want to test many copies of the lens you want to buy? Do you want a huge variety of products where you can look and try? Do you want to buy from someone who holds huge inventory? Your best bet is Cathay Photo or Alan Photo.
Do you want good pricing, and personable service from the a lady boss herself? Then your best bet is MS Color at S11 in AMK
I have to warn you though, that personal experiences may vary. Your experience in a store may vary greatly from another's experience. And pricing will also vary depending on how well you know the staff/boss, who you actually talk to in the store, the demand and supply for a certain product. So do your homework. Look at the price guide someone already posted to you. Get to know the prices. Then, call and email for quotes from the shops listed. Go to the one you fancy the most.
Nothing is perfect in this world, and no retail store is perfect.
Good luck on your purchase. And remember to bring your own camera body in to test the lens. Some lens may work very very well on a certain camera and may totally suck on yours.